6.5 Neurons and synapses

Essential Idea: Neurons transmit the message, synapses modulate the message

Understandings:

Neurons transmit electrical impulses.
The myelination of nerve fibres allows for saltatory conduction.
Neurons pump sodium and potassium ions across their membranes to generate a resting potential.
An action potential consists of depolarization and repolarization of the neuron.
Nerve impulses are action potentials propagated along the axons of neurons.
Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to reach the threshold potential.
Synapses are junctions between neurons and between neurons and receptor or effector cells.
When presynaptic neurons are depolarized they release a neurotransmitter into the synapse.
A nerve impulse is only initiated if the threshold potential is reached.

Applications:

Application: Secretion and reabsorption of acetylcholine by neurons at synapses.
Application: Blocking of synaptic transmission at cholinergic synapses in insects by binding of neonicotinoid pesticides to acetylcholine receptors.

Skills:

Skill: Analysis of oscilloscope traces showing resting potentials and action potentials.

Nature of science:

Cooperation and collaboration between groups of scientists—biologists are contributing to research into memory and learning.

Higher functions of the brain including memory and learning are only partly understood at present and are being researched very actively. They have traditionally been investigated by psychologists but increasingly the techniques of molecular biology and biochemistry are being used to unravel the mechanisms at work. Other branches of science are also making important contributions, including biophysics, medicine, pharmacology and computer science.

Theory of knowledge